Syntheses, crystal structures, and magnetic properties of a series of cyanide-bridged trinuclear chromate(III)−nickel(II)−chromate(III) complexes based on dicyanidechromate(III) building blocks

•Four new cyanide-bridged Cr(III)–Ni(II) complexes have been synthesized.•Four complexes have similar sandwich-like trinuclear structures.•All four complexes display overall ferromagnetic coupling.•The larger the Ni–NC bond angle, the stronger the Ni⋯Cr magnetic interaction.

Four cyanide-bridged trinuclear CrIII−NiII−CrIII complexes [Ni(cyclam)][Cr(bpb)(CN)2]2·2H2O (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane, bpb2– = 1,2-bis(pyridine-2-carboxamido)-benzenate), [Ni(cyclam)][Cr(bpClb)(CN)2]2·4H2O (2) (bpClb2– = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate), [Ni(cyclam)][Cr(bpmb)(CN)2]2·4H2O (3) (bpmb2– = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate) and [Ni(cyclam)][Cr(bpdmb)(CN)2]2 (4) (bpdmb2– = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate) have been synthesized by the reaction of [Ni(cyclam)](ClO4)2 with a series of dicyanidechromate(III) building blocks. Single crystal X-ray diffraction analyses show that the four complexes have similar trinuclear structures with CrIII–CN–NiII–NC–CrIII linkages. Magnetic investigations indicate the ferromagnetic coupling between Cr(III) and Ni(II) centers through the cyanide bridge, with JCrNi = 4.64(3) cm−1 for 1, 4.33(4) cm−1 for 2, 3.57(3) cm−1 for 3 and 5.3(1) cm−1 for 4. The study on magneto-structural correlation for cyanide-bridged CrIII−NiII systems reveals that the cyanide-bridging bond angle is related to the strength of magnetic exchange coupling: the larger the Ni–NC bond angle, the stronger the Ni⋯Cr magnetic interaction.

Graphical abstractFour new cyanide-bridged sandwich-like trinuclear CrIII−NiII−CrIII complexes were synthesized based on a series of dicyanidechromate(III) building blocks. Magnetic investigations on the four complexes indicate the existence of ferromagnetic coupling between Cr(III) and Ni(II) centers. The study on magneto-structural correlation reveals that the larger the Ni–NC bond angle, the stronger the Ni⋯Cr magnetic interaction.Figure optionsDownload full-size imageDownload as PowerPoint slide